This invention relates to a laser light source device, an optical information recording device, and an optical information reproducing device.
In order to cope with the recording capacity of digital information increasing year after year, high-density optical discs are proposed to the industry, such as Blu-ray Disc (BD) Specification utilizing a disc media in combination with semi-conductor laser of 405 nm-range wavelength, high-NA objective lens with 0.85 numerical aperture (NA), and cover glass of 0.1 mm thickness, and High-Definition Digital Versatile Disc (HD-DVD) Specification utilizing a disc media in combination with semi-conductor laser of 405 nm-range wavelength, 0.65 NA, and cover glass of 0.6 mm thickness.
BD and HD DVD recorders, players and drives for PCs have already been put on the market in the expectation that these devices will become popular in the market replacing the current DVD products in the near future.
This conventional optical storage technology like BD and HD DVD has increased capacity by shortening wavelength and increasing numerical aperture of objective lens. However, when we aim to improve recording capacity further, these methods are no longer effective because wavelength is already well short and NA of objective lens is already enough large. Therefore, various research institutes have proposed several future technologies to increase recording capacity dramatically.
Among many of the future technologies, one of promising candidate is the hologram recording technology.
For example, Japanese Patent Application Laid-open Publication No. JP 2006-114183-A discloses the hologram recording technology partly.